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Full text of "Text Book Of Mechanical Engineering"


Appendix VI.

Height of neutral axis from H = ^ = 275

24*57

io8r

bh*
Using the general formula   I., =------1- ax"

2nd moment of n = 31-----+ ^-$ x 36)     = 126*29

8xrs3      /
A =   -j2      +(12x2-75)   =   32-44

H =. * *? 5   + (7*5 x i'75a) =   57'S

b/fi
2nd moment of c =  + ax1

36

- 'S^6'S8 + (i'87x-S3)  =     6-26
Total value of 2nd moment    =     22279

.-. Moment of resistance = A ~~

JFt    

I'2^X222'8

=     -^~~           == 79 ton ins.

O D

The wrought-iron beam has the neutral axis at its centre.
We will therefore take the 2nd moment of j + E 4- F and
double it, afterwards adding that of G.

2nd moment of j

7 x X'5

-^

+(3'5X4*752)   = '79*073

E = till. 4. (2-25x4-252)

12

'C X *\

2nd moment of G = -3....P
12

5S +

Doubled

Total value of 2nd moment    =
. . Moment of resistance = /t -

= 5     -.9^5. ._ 292 tons ins.

= 24*02
143-640
287-28

J'2

292*48